登录常用的js

        <input type="text" maxlength="50" autocomplete="off"             value="请输入用户名"              onfocus="if(this.value=='请输入用户名') this.value='';            this.className='inputstylefocus';return true;"            onblur="if(this.value=='') this.value='请输入用户名';            this.className='inputstyle';return true;">                    <input type="password" maxlength="20"             value="+_-_-_+"              onfocus="if(this.value=='+_-_-_+') this.value='';            this.className='inputstylefocus';return true;"            onblur="if(this.value=='') this.value='+_-_-_+';            this.className='inputstyle';return true;">